This invention relates to documents, and more particularly, but not exclusively to methods of producing documents which have an information carrier with a multiplicity of storage positions, wherein selected storage positions are provided with machine-readable information.
Documents such as identity cards, credit cards, securities, cheques, travel tickets, entrance cards and the like, with machine-readable information thereon, are known in various forms. Most of the documents which are usually employed nowadays, which have coded information in the form of magnetic or optical markings, can be forged at relatively small cost.
A very high degree of security from forging is achieved in a known machine-readable document which contains a hologram, which has the holographic image of a reference number which is binary coded by a given pattern of light spots which are delimited from each other. Such a hologram which includes a coded reference number and information concerning genuineness can be relatively easily read and tested for genuineness, by a machine. On the other hand, maufacture of such a hologram requires thorough technical knowledge and expensive technical aids, which are not readily accessible, so that forgeries which are likely to be successful can only be achieved at very high cost. In a document with such a hologram, the reference number is incorporated at the stage of the holographic recording of the pattern of light spots, that is to say, at an early stage in the production method. This means that a separate hologram must be produced for each document with which an individual reference number is to be associated, and the individual numbers of a series of documents must be known to the producer of the hologram.
According to the present invention there is provided a method of producing a document which has an information carrier with a multiplicity of storage positions, wherein selected storage positions are occupied by respective machine-readable optical markings, which markings cause a predetermined modification of incident light and whose geometrical position on the information carrier represents coded information, in which method a said optical marking is introduced into each storage position, and, subsequently, selected said optical markings are cancelled or altered.